The geochemistry and isotope systematics of Archean greenstone belts provide important constraints on the origin of the volcanic rocks and tectonic models for the evolution of Archean cratons. The Kam Group is a ∼10‐km‐thick pile of submarine, tholeiitic mafic, and subordinate felsic volcanic rocks erupted between 2712 and 2701 Ma that forms the bulk of the Yellowknife greenstone belt in the dominantly granite‐metasedimentary Slave Province. Mafic rocks range from Normal‐mid‐ocean range basalt‐like basalts to slightly light‐rare‐earth‐element‐enriched (LREE‐enriched) but Nb‐depleted basaltic andesites and andesites, whereas dacitic to rhyodacitic felsic rocks are strongly LREE‐enriched and highly depleted in Nb. The \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$\varepsilon ^{T}_{\mathrm{Nd}\,}$$ \end{document} range from +5 to −3 in the mafic to intermediate rocks and from 0 to −5.5 in the felsic rocks. The \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$\varepsilon ^{T}_{\mathrm{Nd}\,}$$ \end{document} decreases with increasing La/Sm, SiO2 and decreasing Nb/La, suggesting that as the mafic magmas evolved they were contaminated by older basement rocks. Gneissic granitoids >2.9 Ga in age, found at the base of the Kam Group, have \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$\varepsilon ^{T}_{\mathrm{Nd}\,}$$ \end{document} between −6 and −9 and are excellent candidates for the contaminant. The geochemical and isotopic data, combined with the submarine eruptive setting and field evidence for existing continental basement, support a continental margin rift model for the Kam Group. Similar geochemical‐isotopic studies are required on other Slave greenstone belts in order to test evolutionary models for the Slave Province.

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加拿大奴隶省耶洛奈夫绿岩带太古宙 Kam 群的地球化学

太古代绿岩带的地球化学和同位素系统学为火山岩的成因和太古代克拉通演化的构造模型提供了重要的约束条件。Kam 群是约 10 公里厚的海底、拉斑性基性火山岩和次级长英质火山岩，它们在 2712 至 2701 Ma 之间喷发，形成了以花岗岩-变质沉积为主的奴隶省的黄刀绿岩带的大部分。镁铁质岩的范围从正常大洋中层玄武岩状玄武岩到轻稀土元素富集（LREE 富集）但 Nb 贫化的玄武质安山岩和安山岩，而英安质至流纹英质长英质岩则强烈富含 LREE并且高度贫化Nb。\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland ,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont } \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$\varepsilon ^{T}_{\mathrm{ Nd}\,}$$ \end{document} 随着 La/Sm、SiO2 的增加和 Nb/La 的减少而减少，这表明随着基性岩浆的演化，它们受到了较老的基岩的污染。片麻岩花岗岩年龄 >2.9 Ga，发现于 Kam Group 底部，有 \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland ,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont } \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$\varepsilon ^{T}_{\mathrm{ Nd}\,}$$ \end{document} 介于 -6 和 -9 之间，是污染物的极好候选者。地球化学和同位素数据，结合海底喷发背景和现有大陆基底的现场证据，支持 Kam 群的大陆边缘裂谷模型。